Biosurfactants (hereinafter also referred to as BS), which are surfactants derived from living organisms, have high biodegradability and a high degree of safety, and are expected to be used industrially as next-generation surfactants.
A sophorolipid (hereinafter also referred to as SL), which is known as a glycolipid-type BS, is a fermentation product obtained from fermentation by yeast. An SL can be easily produced by, for example, inoculating yeast on a liquid medium containing carbon sources, such as sugars including glucose, and vegetable oils and fats, and stirring the medium while aerating the medium at a mild temperature and under pressure. Since SL has greater productivity (for example, about 100 g/L) than the other BS, it is widely used in industrial fields (Non-patent Document 1, Patent Document 1). Further, since SL is highly safe for the human body, SL has also been applied to detergents for dish-washing machines, and to cosmetics (Patent Document 2).
Further, in order to expand the application of SL, a great deal of research is currently being conducted, including concerning SL production by fermentation under different medium conditions (in particular, carbon sources) (Non-patent Documents 2 and 3), or chemical synthesis of SL derivatives (Patent Document 3).
However, there are general concerns regarding adverse environmental consequences or safety during the chemical synthesis of compounds. Nowadays, in view of LCA (Life-Cycle Assessment), the establishment of safer production methods, including raw material production, is recognized as important. Therefore, for the SL as well, which is derived from natural products and is thus considered highly safe, it is important to establish a production method that does not require the use and discharge of toxic organic solvents.